This invention is related to the field of ethylene polymerization.
Approximately 20 billion pounds of polyethylene is produced each year in the United States. A portion of this polyethylene is produced in the form of "fines". Polyethylene fines are generally particles that are so small they can pass through a 100 mesh screen. This means that the polyethylene fines are smaller than about 150 micrometers or about 0.006 inches. These polyethylene fines can be up to about 15 weight percent of the polymerized product. Usually, these fines are subjected to a compounding step wherein the fines are compounded into larger particles. This compounding step, however, is an additional expense that could decrease the polyethylene producer's ability to compete in the global polyethylene market. Therefore, if the amount of fines generated could be lowered, a significant cost savings could be realized because the resin could be sold as fluff or powder.
As with any process to produce a product, it is desirable from an economic viewpoint to perform as few manipulative steps on the product as possible. In the case of polyethylene, it would be preferable to sell the polyethylene resin as fluff or powder from the reactor. This would eliminate such operations as extruding and pelletizing. However, if the fluff is not compact enough, that is, if the fluff has a low fluff bulk density, it can be uneconomical to transport the fluff to the customer. Therefore, if the fluff bulk density of a polyethylene composition could be raised to a higher level, a significant cost savings could be realized.